It might be cheaper to use Kodak's Flexicolor fixer. From B&H and Adorama you can get enough concentrate to make 5 gallons for about $8 US without the fuss and bother of shipping and storing 25kg. of sodium thoisulfate. The stuff works and works well.

As I mentioned in my post, I'm in Australia, and there aren't any cut-price outlets on this side of the Pacific Ocean. We are lucky to have a good range of photo products available, but prices are a lot higher than you pay. Bulk chemicals, on the other hand, are fairly easy for me to collect in the car. There is certainly inconvenience in storing and mixing. Last time I priced the bulk chemicals, Ole's Fixer was about 30% of the cost of ready made.